Synthetic Fibres and Plastics

Q41. Why plastic finds such a variety of uses?

Ans. The fact is that plastic is easily mouldable i.e. can be shaped in any form. Plastic can be recycled, reused, coloured, melted, rolled into sheets or made into wires. That is why it finds such a variety of uses.

Q42. Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.

Ans. The handle and bristle of a toothbrush should not be made of same material as the handle of the toothbrush should be hard and strong while the bristle should be soft and flexible.

Q43. List the characteristics of synthetic fibres which make them popular dress materials.
Or
What are characteristics of synthetic Fibres?
Or
Mention the general characteristics of synthetic plastics.

Ans. Synthetic fibres possess unique characteristics which make them popular dress materials. They dry up quickly, are durable, less expensive, readily available and easy to maintain.

Q44. Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Ans. Rana should buy cotton shirts for summer because cotton absorbs sweats away from the body and helps eliminate moisture buildup between clothes and skin in order to keep the body dry.

Q45. Explain why some fibres are called synthetic.

Ans. Some fibres are called synthetic because they are made by human beings by chemical processing.  Such fibre is made up of small units that join together to form long chains. Each small unit is actually a chemical substance.

Q46. Give three advantages of polythene over natural materials.

Ans. Three advantages of polythene over natural materials are:

                         i.        It is light, strong and durable.

                        ii.        It can be rolled into sheets.

                       iii.        It does not react with water and air.

Q47. How is rayon made? Write two advantages of using rayon.
Or
What are the advantages of artificial silk over natural silk?

Ans. Rayon is obtained by chemical treatment of wood pulp.

Advantage

                         i.        It is cheaper than silk and can be woven like silk fibres.

                        ii.        It can also be dyed in a wide variety of colours.

Q48. ‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment

Ans. Natural fibres are obtained from plants and animals, which means cutting off lots of trees. This leads to deforestation. But synthetic fibres are obtained by chemical processing of petrochemicals and hence help in conservation of forests.

Q49. Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plug boards

Ans. a. Saucepan handles are made of thermosetting plastics because it is a poor conductor of heat.

b. Electric plugs/switches/plug boards are made of thermosetting plastics because it is a poor conductor of heat and electricity.

Q50. What properties of plastics make them so useful?

Ans. Characteristic properties of plastics

                         i.        Plastic is non-reactive

                        ii.        Plastic is light, strong and durable

                       iii.        Plastics are poor conductors

Q51. Why is a plastic bucket preferred over an iron bucket?

Ans. Plastic bucket preferred over an iron bucket because

                         i.        Plastic is non-reactive

                        ii.        Plastic is light, strong and durable

                       iii.        Plastics are poor conductors

Q52. What are some uses of nylon?

Ans. Uses of Nylon

                         i.        Nylon is used to make articles such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains etc.

                        ii.        It is also used for making parachutes and ropes for rock climbing.

Q53. Why is acrylic fibre more popular than wool?

Ans. Acrylic fibre is more popular than wool because

                          i.        Clothes made from acrylic are relatively cheaper.

                         ii.        They are available in a variety of colours.

                        iii.        Synthetic fibres are more durable.